Update dependency sinon to ^8.1.0

Created by: renovate[bot]

This PR contains the following updates:

Package	Type	Update	New value	References	Sourcegraph
sinon (source)	devDependencies	minor	^8.1.0	homepage, source

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Release Notes

sinonjs/sinon

v8.1.0

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• Support negative indices in getCall (#​2199)

v8.0.4

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• Remove misleading 'own' from exception message

v8.0.3

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• Move .printf to proxy

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